This invention relates to method and apparatus for recovering hydrocarbon constituent elements of an earth aggregate and will particularly relate to methods and apparatus for releasing the hydrocarbon constituent elements of the earth's aggregate from the earth aggregate matrix by establishing an electrical field through the earth aggregate which electrochemically reacts to break the intermolecular bond between the hydrocarbon constituent element and the earth aggregate matrix.
As used herein, "hydrocarbon constituent elements" includes oil, bitumens (such as the asphaltic tars and bitumens found in the Athabasca "tar-sands"), kerogens (such as found in oil shale), and coal, or any other earth aggregate having a fossilized mineral hydrocarbon content. While the preferred embodiments will be described with respect to release of the tar and bitumen contained in the "tar sands", the processes are applicable to recovery of all other hydrocarbon constituents. "Bitumen", as used herein includes all of the fossilized hydrocarbons above-described.
There are numerous deposits of tar and bitumen world-wide which occur on or so near to the surface that it is possible to recover the tar and bitumens by mining on or from the surface. The material recovered is, of course, a mixture of earth material and tar or bitumen which must be separated into the component parts, with the earth materials to be discarded and the bitumens to be saved for further processing and refining.
Such a deposit is found in Alberta Province, Canada, in the Athabasca "tar-sands". The existence of the Athabasca deposits has been known for centuries. Records indicate that the sands were used as a paving material as early as 1915, and first commercial production of bitumen from the sands was achieved in 1930 and the product used as a roofing material. However, notwithstanding the magnitude and problems of the mining operation by itself, the present de-sanding and refining processes are expensive and very complex, involving the use of steam, hot water and corrosive additives. Additionally, Canada has the problem of extremely low temperatures which persist for many months, and perma-frost is nearly always present, compounding the problems of recovering bitumen by conventional thermal means.
The Athabasca tar-sands are located in the northern half of Alberta Province and have been estimated to contain up to 893 billion barrels of bitumen, of which about 350 billion, or 30 to 35%, is recoverable by today's known technology. These sands are a series of quartz sand deposits impregnated with varying amounts of a heavy, highly viscous bitumen. Sands are deposited on an irregular surface of limestone or shale and are generally overlain with overburden. Once the tar-sands have been mined by open pit techniques, bitumen extraction is conventionally accomplished by the hot water process. Although a simple process, it is sometimes extremely difficult to control.
Basic bitumen recovery is accomplished in a very short period of time by mixing the mined tar-sands with water and caustic soda at 180.degree. F. in a slowly rotating drum into which live steam is sprayed below the surface of the slurry formed therein. The tar-sand disintegrates, liberating bitumen from sand and clay particles. The sand is water-wetted in its natural state which allows fairly clean separation of bitumen in the next step. The slurry leaving the conditioning drum is passed over a vibrating screen where clay lumps and rocks, forming a portion of the earth's aggregate, are removed with the slurry delivered into a separation cell, where sand particles settle quickly to the bottom and the bitumen floats to the surface of the cell for recovery. The bitumen is then further processed to completely remove water and other minerals.
The bitumen thus obtained is a highly viscous, tarry, black material having an API gravity of about 9.degree. and contains about 5% sulphur, plus trace amounts of heavy metals such as nickel, vanadium, and iron. With these characteristics, it is not suitable for market use and must be further processed before it can be utilized. Processing is carried out using a "fractionating" or "cracking process" similar to "fractionating" crude oil.
The above-described prior art process for releasing bitumens from the tar-sands requires the use of caustic solutions, thermal heating, and steam generating capability in a geographic area having extremely low temperatures for several months at a time, necessitating complex insulated process plants.
Further, the bitumen recovered is still extremely viscous with poor flow capability that is further compounded by the low temperatures encountered.
The present invention overcomes the deficiencies of the prior art by providing methods and apparatus for releasing the hydrocarbon constituents of an earth aggregate matrix without requiring the use of corrosive additives or live steam processing.